JCMT supports STEM Fest 2018 for Big Island Girl Scouts

The EAO Outreach Team was thrilled to be invited to help out at the 2018 STEM Fest event held in Waimea at the Kahilu Town Hall for Big Island Girl Scouts. The event, attended by 75 girls on November 17th, provided the opportunity to experience hands on activities from a variety of science and engineering fields.

JCMT staff members Alexis Achohido and Mimi Fuchs worked with Girl Scouts to discover how astronomers know what stars are made of. In particular we highlighted the work of  Cecilia Payne-Gaposchkin, who proposed a theory for the composition of stars in her 1925, her PhD Thesis!

As well as looking at what stars are made of we also looked at what dense interstellar dust clouds are made of and made our very own candy molecules.

Maunakea Wonders Teachers Workshop

The third Maunakea Wonders Teacher Workshop began on October 17th at the University of Hawai’i’s Department of Education in Hilo. Throughout the second half of October, we have the incredible opportunity to share fun astronomy activities and resources with the future teachers of Hawai’i. Despite the frigid weather, this included on-site tours of the JCMT and UKIRT where we had a blast talking about the different functions of each telescope on the mountain. We are looking forward to more fun and excitement on campus on October 31st – Mahalo nui loa to this vibrant group of educators!


Maunakea Gender Equity and Diversity Survey 2018 Report

In July 2018, the Maunakea Gender Equity and Diversity Committee distributed a survey to the staff at the Maunakea astronomical organizations. The survey was intended to invite opinion on the current state of equity and diversity in the Maunakea astronomy community and seed conversation and ideas for enhancing diversity and inclusion in our organizations across our islands.

The report on the results of the survey is here:

Maunakea Gender Equity and Diversity Survey 2018 Report

and the Appendix A, listing the survey questions, is provided for reference:

Gender Equity and Diversity Survey questions

The first results are presented by Jessica Dempsey at the Maunakea Users’ Meeting on October 4th, 2018. A PDF of the talk is linked here for convenience. For usage or distribution of these data, please contact Jessica Dempsey: j.dempsey “at” eaobservatory.org.

Photo by Oro Whitley

– 20181004


Discovering Magnetized Inflow Accreting to the center of Milky Way Galaxy – An important force to transport gas to the supermassive black hole Sagittarius A*

Is magnetic field an important guiding force for gas accreting to supermassive black hole (SMBH) — for example, the one that our Milky Way Galaxy hosts? The role of magnetic field in this subject is little understood and trying to observe it has been challenging to astronomers. Researchers at the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), Taiwan, led by Dr. Pei-Ying Hsieh, have utilized a measurement of high resolution data by using the instruments on the James Clerk Maxwell Telescope (JCMT). Their result provides clear evidences in showing that the orientation of the magnetic field is in alignment with the molecular torus and ionized streamers rotating with respect to Sagittarius A* – the black hole our home galaxy hosts. The findings are published in Astrophysical Journal in 2018 August 2nd (2018, ApJ, 862, 150).

Color-composite images of the SMA map tracing the molecular gas of the CND (blue) and the Very Large Array (VLA) 6 cm map tracing the mini-spiral (red). The magnetic field of the JCMT-SCUPOL data and the model are overlaid with the white segments in the upper right and low left panel, respectively. The location of SgrA* is labeled with the black cross. The CND is a molecular torus (ring) rotating with respect to the supermassive black hole SgrA* in our Galaxy. The mini-spiral is hypothesized to be originated from the inner edge of the CND. The alignment of the magnetic field line along with the CND and the mini-spiral tells us that they are linked with a coherent magnetic field. The team found the magnetic field is able to guide the ionized particles from the CND to the mini-spiral, which suggests a picture the footprint of inflow near SgrA*. In the lower right panel, the latest dust polarization data taken in 2017 measured with the new instruments POL-2 installed in JCMT is shown. The magnetic field is shown with the white segments. An improved spatial coverage and sensitivity clearly reveal the connection between the CND and the mini-spiral at even higher spatial sampling than the JCMT-SCUPOL data, which confirm the picture the team proposed.

SgrA* – the best laboratory to study black hole feeding in the sky

Sagittarius A* (SgrA*),  being the closest SMBH in our home in the universe, the Milky Way Galaxy, has been targeted by many scientists to understand the nature of gas accretion in the past decades. Observing the gas accretion onto SMBH is critical to help us to understand how it releases tremendous energy.

The circumnuclear disk (CND) is a molecular torus rotating with respect to SgrA*, within which are the ionized gas streamers called mini-spiral (also called SgrA West) filling the molecular cavity. The mini-spiral is hypothesized to be originated from the inner edge of the CND. The CND, being the closest “food reservoir” of SgrA*, is therefore critical on the understanding of the feeding of SgrA*. However, looking for the physical evidences to connect the CND and the mini-spiral puzzles astronomers since they were discovered a few decades ago.

Intensive measurements of dynamical movements orbiting SgrA* have been done in the past decades, but another important force – the magnetic field – is rarely probed. This is solely because the weak polarized signal generated by the magnetic field from dust emission is difficult to measure. However, the magnetic field is expected to be important for material orbiting within and around the CND as the magnetic stress acting on the rotating disk can exert a torque to extract angular momentum from rotating gas, and thus drive gas inflows. Besides, The magnetic tension force is also possible to draw the gas back from the gravitational pull. Taking advantage of excellent atmospheric conditions of Mauna Kea summit at 4000 m, and large aperture size of the JCMT (15 m in diameter), the submillimeter polarization experiments were successfully obtained toward the Galactic Center to understand the role of magnetic field.

Tracing Magnetized Accreting Inflow

The team utilized the dust polarization data obtained by the JCMT-SCUPOL instrument to image the orientation of the magnetic field. A detailed comparison with higher-resolution interferometric maps from the Submillimeter Array (SMA) reveals that the magnetic field aligns with the CND.  Moreover, the innermost observed magnetic field lines also appear to trace and align with the mini-spiral coherently. This is the first attempt to reveal the footprint of inflow linking the CND and the mini-spiral since they were discovered a few decades ago. The comparison of the model and data reinforces the key idea that the CND and the mini-spiral can be treated as a coherent inflow-system.

The team found that the magnetic field is dynamically significant towards the CND and the mini-spiral. This finding tells us that the magnetic field is able to guide the motion of the ionized particles originated in the CND, and produce the observed spiral pattern of the mini-spiral. Dr. Hsieh said, “We found the magnetic field is critical to explain the inflow structure and will also help to understand the inflow picture in other galaxies hosting black hole similar to SgrA*. “

Paper and research team:

These observation results were published as Hsieh et al. “A Magnetic Field Connecting the Galactic Center Circumnuclear Disk with Streamers and Mini-spiral -Implications from 850 micron Polarization Data” in the Astrophysical Journal (published in the Astrophysical in August 2nd).

This research was conducted by:

Hsieh, Pei-Ying (ASIAA); Koch, Patrick M. (ASIAA); Kim, Woong-Tae (SNU); Ho, Paul T. P. (ASIAA; EAO); Tang, Ya-Wen (ASIAA); Wang, Hsiang-Hsu (CUHK)

This research is supported by the Ministry of Science and Technology (MoST) of Taiwan through the grants MoST 105-2811-M-001-141, MoST 106-2811-M-001-136, MoST 104-2119-M-001-019-MY3, MOST 105-2112-M-001-025-MY3, Academia Sinica Career Development Award, and the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST; No. 3348-20160021).

Related Links:




Call for Proposals 19A

The East Asian Observatory is happy to invite PI observing proposals for semester 19A at the JCMT. Proposal submission is via the JCMT proposal handling system, Hedwig. For full details, and for proposal submission please see


The 19A Call for Proposals closes on the 15th of September, 2018.

If this is your first time using Hedwig, you should ‘Log in’ and generate an account. There is a Hedwig ‘Help’ facility at the upper right corner of each page, and individual Help tags in many other places.

Please contact us at helpdesk@eaobservatory.org if you have remaining questions.

– 20180815

Mahalo to Mailani Neal!

The East Asian Observatory wishes to extend a big mahalo to our summer intern Mailani Neal for her excellent work tracking temperature changes across the JCMT’s dish!

We are grateful for all her hard work and we wish her all the best as she enters her final year at Rensselaer Polytechnic Institute in New York!

This gif shows an example of the telescope’s changing temperature over one night in June, 2018:

This analysis is important for understanding calibration observations and the effect of the weather on all the data we collect.

Mahalo, Mailani!

– 20180807

POL-2 data reduction fix for source blurring

POL-2 is the JCMT’s sub-millimeter polarimeter working at both 450 and 850 microns. POL-2 is a polarimeter not a detector, and so requires SCUBA-2 for use. It is used to trace the alignment of dust particles at sub-millimeter wavelengths and thus the magnetic field orientation and strength (with some additional physics added into the mix) of regions in our Universe!

Recently it has been found that sometime there is a loss of synchronisation between data values and pointing information in the data reduction process (CALCQU, run by pol2map as part of step 1). This loss of synchronisation is triggered by anomalous values in the array of HWP (Half Wave Plate) angles stored in the raw data. The result is blurring (or smoothing) of sources in some POL-2 maps (see figure below).

The fix is to download our rsync this build of the starlink software and re-reduce your data. If you look at your re-reduce data you may find that some of your maps improve, depending on whether any of your observations suffered from the blurring problem. The size of the improvement will depend on how many blurred observations you have.

For regions where multiple observations were used to produce the final maps the issue may have been less pronounced if obsweight=yes was used.

In addition, users wishing to reduce POL-2 450 micron data are asked to ensure the data have been reduced using the latest starlink 2018A software prior to this release there was a bug in the software which caused a 4 degree difference  in the angular zero point at 850 and 450, so all 450 vector maps produced so far will have a systematic error of 4 degrees in the vector angle, unless updated software (rsync starlink or 2018A starlink) was used.

The image shows two total intensity maps made from an observation of OMC1. Left: before the fix for blurring. Right: after the fix for blurring.

Also did you know you can combine various I maps into a cube to view as a movie? You can do this (assuming you ran pol2map with “mapdir=maps”) by running:


paste in=maps/\*Imap out=Icube shift=\[0,0,1\]

gaia Icube

Then in gaia, in the pop-up window that holds the cube visualisation controls, drag the “Index of plane” slider left or right to step through the planes in the cube!

You can do the same for the Q or U maps by replacing “I” with “Q” or “U” above (note, that’s an upper case “I” for the externally masked I maps – use a lower case “i” for the auto-masked I maps).

– 20180724

SMU work and data checks

In May our engineering staff undertook major maintenance work of the Secondary Mirror Unit on the JCMT. After this work it was noted that the Secondary mirror was sometimes vibrating, which lead to beam deformation. This was noticed due to sporadic increased FCF values – and could also be seen in the aspect ratio of our calibrators (see image below). Observers who collected data between UT dates May 24th 2018 and 08:10UT on June 30th 2018 should be aware of this issue. Astronomers who may have affected observations should check their data closely. This issue was noted to be intermittent. If you have questions about the data quality please contact your Support Scientist or the observatory directly.

On June 30th, we applied a temporary work-around to account for these SMU vibrations. To implement a more permanent solution, the observatory briefly removed the GoreTex membrane to work on the Secondary Mirror Unit. This work was performed between Tuesday July 24th, and Monday, July 30th.  The PI and Large Program time were unaffected.

Below is a plot showing the aspect ratios of calibrator CRL 2688 over time. The blue, shaded region represents the nominal values. Note that the high aspect ratios observed in between the temporary and permanent fix (boxed in red) were part of a low elevation, poor weather (wet grade 5), poor seeing engineering and commissioning project. Regular observing was unaffected.


 – 20180815

CHIMPS-2 members meet in Liverpool

Members of the CHIMPS-2 Large Program met for a two day meeting in Liverpool on June 28th and 29th. The meeting covered data collection, reduction and analysis with astronomers from all over the globe. For more information on the CHIMPS-2 project click here. We wish the team “clear skies” as they look to expand the JCMT CO heterodyne data towards the Galactic Centre this summer.

– 20180708